Only convert valid SharedMemInfo

This CL avoids passing nullptr to underlying HAL and cause
SEGFAULT.

Bug: 37589989
Test: compiles and VTS passing
Change-Id: Ic44409e64466e54a3a3027721897c0755ba34fc7
Merged-In: Ic44409e64466e54a3a3027721897c0755ba34fc7
1 file changed